1. Failure DescriptionThe task was to expand the Linux file system per the customer's request. During the process of mapping the hard disk, creating the PV, and adding it to the VG, an "unknown device" error was encountered.
bash[root@KMS-Svr cache]# pvs
Incorrect metadata area header checksum on /dev/sdb1 at offset 4096
Couldn't find device with uuid ZPy1sa-fXhe-qrcQ-HFhi-eazU-4Mg3-toY3Xv.
PV VG Fmt Attr PSize PFree
/dev/sda2 vg_testkmssvr lvm2 a-- 149.51g 0
/dev/sdb1 lvm2 a-- 499.99g 499.99g
/dev/sdc1 vg_testkmssvr lvm2 a-- 100.00g 0
/dev/sdd vm2t lvm2 a-- 2.00t 0
/dev/sde vm2t lvm2 a-- 2.20t 0
/dev/sdf1 vm2t lvm2 a-- 2.00t 0
/dev/sdg vm2t lvm2 a-- 2.00t 0
/dev/sdh vm2t lvm2 a-- 2.00t 0
/dev/sdi vm2t lvm2 a-- 2.00t 0
/dev/sdj vm2t lvm2 a-- 2.00t 0
/dev/sdk1 vm2t lvm2 a-- 1.86t 74.36g
/dev/sdk2 vg_testkmssvr lvm2 a-- 140.64g 19.63g
unknown device vm2t lvm2 a-m 2.00t 2.00t2. Troubleshooting
1. Log AnalysisNo specific errors were found in the messages log. However, dmesg logs indicated the following:
bashsd 2:0:12:0: [sdl] Very big device. Trying to use READ CAPACITY(16).
sd 2:0:12:0: [sdl] Cache data unavailable
sd 2:0:12:0: [sdl] Assuming drive cache: write throughThis showed the disk was recognized at the OS level. The customer confirmed that this disk was used on a different host, which was taken offline. The engineer assumed old VG/PV information was still stored on the disk.
2. Removing Problematic DisksRunning vgreduce to remove missing devices:
bash[root@KMS-Svr cache]# vgreduce vm2t --removemissing
Incorrect metadata area header checksum on /dev/sdb1 at offset 4096
Couldn't find device with uuid ZPy1sa-fXhe-qrcQ-HFhi-eazU-4Mg3-toY3Xv.
Wrote out consistent volume group vm2tAfter running vgreduce, the disk status appeared normal, but it could not be displayed using pvs. The fdisk -l command showed the disk:
plaintextDisk /dev/sdl: 2199.0 GB, 2199023255552 bytes
Device Boot Start End Blocks Id System
/dev/sdl1 1 267349 2147480811 8e Linux LVMUsing lsblk, the system showed disk sdl and partition sdl1, so PV recreation was required.
3. Recreating the PVRunning the command:
bashpvcreate /dev/sdl1 --forceThe pvs command confirmed the PV creation was successful. Then, the vgextend command added /dev/sdl1 to the VG:
bashvgextend vm2t /dev/sdl13. Lessons Learned
When "unknown device" errors occur, running vgscan to rescan LVM block devices can help. Exclude problematic PVs from the VG to restore VG functionality.
4. Additional Knowledge